Pneumoniae, Herpes simplex virus (HSV), Enterovirus and Parechovirus PCR is routinely available for Neisseria meningitidis, Streptococcus.There is progressive reduction in both neutrophils and lymphocytes after 4 hours Delays in laboratory analysis of CSF can alter the cell count as a result of lysis in the CSF.Consider subarachnoid hemorrhage when there is unexplained or persistent RBCs in CSF.Some guidelines suggest that in traumatic taps, the white blood cell and protein count can be corrected based on the following calculation: 1 white blood cell for every 500–700 red blood cells and 0.01 g/L protein for every 1000 red cells.If there are more white cells than the normal range for age, then the safest option is to treat The safest interpretation of a traumatic tap is to count the total number of white cells, and disregard the red cell count.Seizures do not cause an increased CSF cell count.Prior antibiotics usually prevent the culture of bacteria from the CSF.Antibiotics are unlikely to significantly affect the CSF cell count or biochemistry in samples taken.If the CSF is abnormal, the safest course is to treat for bacterial.Neutrophils may predominate in viral meningitis, even after the first 24 hours.A predominance of lymphocytes does not exclude bacterial meningitis.Gram stain may be negative in up to 60% of cases of bacterial meningitis, even without prior antibiotics.In the case of a traumatic tap, rules based on a predicted white cell count in the CSF are not reliableĬSF is abnormal the safest course is to treat as if it is bacterial meningitis.The presence of any neutrophils in the CSF is unusual in normal children and should raise concern about bacterial meningitis.The use of CSF for other purposes (including the diagnosis of specific neurological conditions, subarachnoid haemorrhage or malignancy) is outside its scope. This guideline aims to help with the interpretation of CSF results for the purpose of diagnosing or excluding meningitis. You can also find additional topics and questions directly from the Knowmedge Internal Medicine ABIM Board Exam Review Questions QVault.Meningitis and encephalitis Meningococcal disease Lumbar puncture Antimicrobial guidelines You can view all the previous ABIM Exam Review Questions of the Week at the Knowmedge Blog. As this patient’s CSF-to-serum glucose ratio is 0.3, the best answer is Choice C (Early bacterial meningitis).Ĭhoice B (HSV encephalitis) would be likely if RBCs were noted in the CSF. If this ratio is less than 0.4, early bacterial meningitis is the likely diagnosis. To distinguish the timeframe of bacterial meningitis, a CSF-to-serum glucose ratio is calculated. This patient’s CSF glucose of 24mg/dL and elevated leukocytes point to a bacterial cause. Like most other viral-caused infections, patients with meningitis will have a negative Gram stain and culture while the majority of patients with bacterial meningitis will have positive results. Similarly, protein levels are lower in viral infections but this is not as definitive as there is overlap in the respective ranges of 100-500mg/dL for bacterial and less than 200mg/dL for viral. A mnemonic for remembering that CSF glucose is lower in bacterial infections (less than 40mg/dl versus greater than 45mg/dL) is that the bacteria eat up the glucose, lowering its level. The differential is a neutrophil-dominant WBC count in bacterial meningitis and a lymphocytic-dominant WBC count in viral meningitis. Leukocyte count is also higher in bacterial cases: 1,000-5,000/µL versus 50-1,000/µL in viral cases. CSF opening pressure is between 200-500mmH 2O in bacterial meningitis while it is less than 250mmH 2O in viral cases. To determine the cause of meningitis, a lumbar puncture with cerebrospinal fluid (CSF) analysis is performed. Two-thirds of patients with bacterial meningitis present with fever, neck stiffness (nuchal rigidity) and altered mental status. This is also the most common form of meningitis. Of the different types of meningitis, the one that requires the most urgent treatment is acute bacterial meningitis. Which of the following is the most likely diagnosis? CSF analysis reveals: 2,000 WBCs/µL, PMN predominance, no RBCs, glucose 24mg/dL and protein 106mg/dL. Lumbar puncture is performed and cerbrospinal fluid (CSF) studies are obtained. Physical exam reveals neck stiffness concerning for meningitis. Give it your best shot and then see below for the answer.Ĥ5-year-old female presents to the ED with fever and headaches, a condition she has been experiencing for the past two days. As we begin #InfDiseaseWeek in our preparation of the ABIM and Internal Medicine Shelf exam review, here is a question directly out of the Knowmedge QVault.
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